The present invention relates to a printing head comprising at least one tubular printing element having a capillary nozzle at one end and communicating at the other end directly with an ink reservoir, the printing element being associated with a piezoelectric transducer for varying the volume of the printing element, the printing element and transducer being disposed in a single block, e.g. being encapsulated in a block of resin in a cavity in a support.
In ink jet heads in which the ink reservoir is directly connected to the nozzles, the presence of bubbles of air in the reservoir represents a major disadvantage which adversely affects operation of the head.
A system has been proposed for removing the bubbles from the reservoir by means of a breather pipe which communicates with a suction pump. That construction is complicated and expensive since it requires an additional tube between the movable head and the vacuum pump which is mounted in a static position on the structure of the printer.